Outside AC unit condenser not shutting off - contactor?

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Old 06-02-18, 11:25 AM
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Outside AC unit condenser not shutting off - contactor?

With thermostat set to off, the outside AC unit continues to run unless I disconnect at breaker box. When I reset breaker to ON, the unit comes back on unless I switch back to OFF at breaker. This is with thermostat in off position, or if it set to shut off automatically at set temperature. Condenser seems to still run/work ok except for not shutting off when its supposed to.

The blower fan inside does not continue to run, only the outside unit.

I tried testing the thermostat by pulling out the yellow Y wire at the tstat, and the outside unit is still running. (I have to disconnect the wire because my tstat is not the type that disconnects from the wall). From what I understand, this means its not a problem with the tstat and it is likely the contactor becoming welded shut?

I just wanted to check if I am on the right track before going any further, and what would be the best way to check/test the contactor if that is likely the culprit.


AC Condenser Model: General Electric Model 21TA936H1F

This is a very old unit, from around 1968, but it has performed great for us and from what I understand these are built very well. We don't have the money to replace with a newer unit, and would rather continue to service where possible.

Thanks
 
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Old 06-02-18, 11:41 AM
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Welcome to the forums.

Wow..... that A/C is from before the internet was invented.
I don't even see a picture of it on the internet.

More than likely the contactor has welded itself together. Disconnect the power at the service disconnect and remove the electrical wiring access panel. May be a bit tough if the screws are rusted in.

Post some pics of what you see inside...... How-to-insert-pictures
 
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Old 06-02-18, 03:40 PM
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Thanks!

Yes, very old! I knew it was from looking, but had never actually looked at the Model info until now and was quite surprised.

I can post some photos but it may not be today as a storm is blowing in.

But this guy actually has a video where he opens one up. I believe its the same, if its not the exact model then it seems generally the same:
https://www.youtube.com/watch?v=9gPmfKiZES4

(edit) Actually that one is not quite a match for mine.. very close, but mine looks like this one:
https://www.youtube.com/watch?v=v_LSyUO2Aj4

There is very little out there about this compressor and I am just hoping finding necessary parts won't be an issue...
 

Last edited by LeeMort; 06-02-18 at 06:38 PM.
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Old 06-03-18, 04:05 AM
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Open the unit, disconnect the contactor coil wire and see if that shuts off the compressor. If it does not replace the contactor. A new one can be purchased for about $10.00 dollars. Wow, that unit was new when I started working on A/C units
 
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Old 06-03-18, 11:35 AM
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Here are some photos... I pushed on the contactor piece and it went down and back up - like the guy does at 52 seconds in this video: https://www.youtube.com/watch?v=9gPmfKiZES4

Although seemed to stick a bit at first maybe. Does the fact it was moving up and down mean its not welded shut?

Let me know if these photos aren't clear enough or showing what is needed










There was a dead snake wrapped around this, as well as what looked like a hornets nest next to it. I noticed for some reason the blue wire is clipped and there is the leftovers of a clipped blue wire and red wire sitting under the lid:






Originally Posted by Steamboy View Post
Open the unit, disconnect the contactor coil wire and see if that shuts off the compressor. If it does not replace the contactor. A new one can be purchased for about $10.00 dollars. Wow, that unit was new when I started working on A/C units
Is the circled wire the coil wire? Sorry for my ignorance

 
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Old 06-03-18, 03:53 PM
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In your picture... the right blue circle is the contactor coil connection. There will be two of them.

If your contactor is not getting stuck in them you need to identify if the compressor is running, the fan is running or both.
 
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Old 06-03-18, 04:38 PM
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Alright I disconnected both contactor coil wires and switched power back on - the condenser remained off.

I hooked the wires back up and decided to go ahead and test it again now, switched power back on breaker box and the condenser remained off.

Turned on AC, condenser started up and then I turned AC to off and condenser remained off.

It appears to be functioning normally now... Could it be because the piece I pushed down on the contactor was maybe partially stuck and I unstuck it? Or could the dead snake coiled in where the power enters the lid have caused some kind of voltage issue?

Should I be prepared to replace the contactor, and either way, could anyone suggest where to buy a replacement contactor for this unit as I am sure it will be needed eventually.

Oh and there also appears to be some leaves and whatnot at the bottom of the condenser inside... would I be ok to vacuum hose these out - is there anything I should be aware of before doing something like this?

Thanks!
 
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Old 06-03-18, 04:52 PM
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That contactor looks bad to me. I would definitely install a new 2 pole 30Amp contactor with a 24VAC coil.

You need some ant granules.
Burnt ants are in that contactor.
 

Last edited by Houston204; 06-03-18 at 06:18 PM.
  #9  
Old 06-04-18, 09:52 AM
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Thanks... I will go ahead and get a new contactor to have ready.. just any 2 pole 30Amp contactor with a 24VAC coil will work - I don't need one like is already installed?

I did notice the ants but I wanted to leave it as is for photos so it would show the condition... ants, snake, old hornets nest.. lots of stuff going on inside this unit. It has not been opened up for a long time
 
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Old 06-08-18, 04:25 AM
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Yes a common 24vac 2p 30amp contactor will work. You do not need it to look like that strange contactor.
 
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